Diet effects on female reproduction in high growth (hg/hg) mice that are deficient in the Socs-2 gene

a
Department of Animal Science, College of Agriculture, University of Mar del Plata CC 276, 7620 Balcarce, Argentinab
Department of Animal Science, University of California, Davis, One Shields Ave, Davis, CA 95616-8521, USA

(Received 27 March 2003; accepted 17 December 2003)

Abstract - The detrimental effect of larger body size on reproductive performance has been well documented in mouse models of overgrowth,
such as Growth Hormone (GH) transgenics. This study describes the reproductive performance of the High Growth (HG) mouse model
of overgrowth. The HG mouse model exhibits overgrowth due to a partially recessive autosomal mutation that increases growth
rate and mature body size. The HG phenotype results from the lack of expression of Socs-2, which negatively regulates GH signaling. C57BL/6J (C57) and congenic C57BL/6J-hg/hg (HG) female mice were fed four diets differing in protein and energy content, starting at 8 weeks of age. A complete reproductive
cycle from mating to weaning was evaluated. HG mice were 40% larger than C57 and had a higher feed intake throughout the experiment.
Significant genotype × diet interactions were detected for growth, body composition and reproductive traits. HG females showed
poor reproductive performance compared to controls as demonstrated by their lower fertility during mating, which was not overcome
by changes in the diet. No differences were detected in litter size, but HG animals exhibited a longer gestation length and
heavier pup weaning weights compared to controls. Reproductive impairment in HG seems to be the consequence of the lack of
Socs-2 independent of the effects of increased body size on reproduction.